A known internal combustion engine disclosed, for example, in JP3423649B which will be hereinafter referred to as Reference 1 includes a separator portion for performing a gas-liquid separation on blow-by gas.
The internal combustion engine disclosed in Reference 1 includes a metallic cylinder block, a metallic auxiliary machinery bracket (an auxiliary machinery attachment member) to which auxiliary machines are attached, and a breather chamber (separator portion). In a state where the auxiliary machinery bracket is fixed to a side wall of the cylinder block, a void portion including an inner wall in a predetermined protruding and recessed form is formed between the side wall of the cylinder block in a recess form and a surface of an attachment portion of the auxiliary machinery bracket in a recess form, the side wall of the cylinder block and the surface of the auxiliary machinery bracket facing each other. The void portion is called the breather chamber to function as the separator portion for separating oil for recovery from blow-by gas that is leaked to a crank chamber from a lower portion of a cylinder. In addition, a portion of a coolant flow passage for cooling the internal combustion engine penetrates through the breather chamber across a conduit wall. Accordingly, heat of coolant warmed or heated by the internal combustion engine is transmitted to the breather chamber to thereby warm or heat the breather chamber (void portion). Water vapor in blow-by gas flowing within the breather chamber is thus inhibited from being condensed.
Nevertheless, according to the aforementioned configuration of the breather chamber in the internal combustion engine disclosed in Reference 1, because the breather chamber (separator portion) is formed by the side wall of the cylinder block in a recess form and the surface of the auxiliary machinery bracket in a recess form facing each other, the inside of the breather chamber is likely to be influenced by an outside air temperature. Specifically, in a case where outside air temperature is low and engine coolant temperature is low at the time of start of the internal combustion engine, for example, the metallic cylinder block and/or the metallic auxiliary machinery bracket are cooled, so that the breather chamber (separator portion) and the inside thereof are inhibited from being easily warmed or heated. Accordingly, immediately after the start of the internal combustion engine, water vapor in blow-by gas flowing within the breather chamber in a cold state appears as dew condensation water that may be easily mixed in oil obtained by the gas-liquid separation within the breather chamber.
A need thus exists for an internal combustion engine and a separator structure of the internal combustion engine which are not susceptible to the drawback mentioned above.